1. Field of the Invention PA0 2. Desription of the Prior Art PA0 embedding the tie rods used to anchor the lower ring; PA0 final fixing of the lower ring and finishing off with the inside wall of the volute suction orifice; PA0 final fixing of the upper ring and finishing off with the inside wall of the volute well.
The present invention concerns a method of interfacing mechanical and concrete components of a pump comprising a concrete volute, having an axial suction orifice in its lower part and a well in its upper part substantially coaxial with said suction orifice, coaxial upper and lower metal rings, which are fixed in respective recesses provided in the concrete of said well and of said suction orifice, respectively, a sealing ring removably attached to said lower ring, a metal cover having an edge removably attached to said upper ring, a vertical shaft supported axially and rotatably mounted on said cover, and a rotor attached to a lower end of said shaft and having a part facing said sealing ring with a small clearance between them.
In volute pumps of routine sizes the volute is generally of metal, usually a casting. Beyond a certain size it may be more economical to make the volute from concrete, however, either using formwork, of wood for example, the outside shape of which corresponds to the inside shape of the spiral conduit of the volute, or using prefabricated concrete components which are assembled on site and which, once fitted together, form the volute. In either case concrete is cast around the formwork or the prefabricated components to form the infrastructure of the pumping station (and simultaneously forming the volute in the case where formwork is used).
The best manufacturing and positioning tolerances that can be achieved in civil engineering works are plus or minus 1 cm. These tolerances are incompatible with the tolerances for positioning the mechanical components of the pump, especially the tolerances for positioning the rotor of the pump relative to the stator. For example, the clearance between the sealing ring and the part of the rotor facing said sealing ring has to be in the order of 1 mm. Thus it is not possible to fix the sealing ring and the cover of the pump, which supports the shaft and the rotor, directly to the concrete, in the suction orifice and in the well of the volute, respectively. This is why, in known concrete volute pumps, the sealing ring and the cover are respectively fixed to a lower metal ring and an upper metal ring that have to be embedded in the suction orifice and in the well of the volute, respectively, at extremely precise position, the lower and upper rings forming the interfaces between the concrete volute and the mechanical components of the pump. To this end, during a first phase the lower ring is first positioned relative to the axis of the volute suction orifice and is then wedged approximately in terms of height and level (horizontality). In this position tie rods for anchoring the lower ring are embedded in the concrete.
During a second phase, and using the cover and the rotor of the pump as a jig, the lower ring is then wedged and finally adjusted relative to the geometrical axis of the pump, on the one hand, and the upper ring is wedged and then finally adjusted relative to the lower ring, on the other hand. During a third phase the lower and upper rings are definitely fixed to the concrete. These successive operations of adjusting and fixing the two rings entail masonry works that are also executed in stages, namely:
These successive operations entailing works of different kinds (masonry and mechanical adjustments) have the disadvantage of requiring repeated and alternating deployment of differently skilled workforces.
Also, in known concrete volute pumps the sealing ring and the cover are supported directly by the lower ring and by the upper ring, respectively. As a consequence of this, apart from the fact that the two rings have to be positioned in a precise manner (with a tolerance of 1 mm or better), they have also to be machined so as to have surfaces of an appropriate shape and with an appropriate surface finish to receive the sealing ring and the pump cover, respectively. These machining operations are relatively complex and costly, given that, here again, the machining tolerances are in the order of 1 mm or better and in that the two rings are relatively large. The diameter of the lower ring depends on the suction diameter of the pump rotor and that of the upper ring depends on the outside diameter of the rotor. To give an idea of the magnitudes involved, these diameters routinely vary between 1.5 m and 4 m.
An objective of the present invention is to propose a method executing, as a single operation and simultaneously, fitting of the lower and upper rings and the formation of mechanical support surfaces adapted to receive the removable components of the pump (sealing ring and cover), without it being necessary to call in specialists in other disciplines than mechanical engineering and without it being necessary to use precisely machined rings.